High-voltage electric circuit breaker with high-speed tripping means

ABSTRACT

Discloses a high-voltage circuit breaker comprising a control device at high potential operable to produce separation of the usual contacts of the breaker, an operator at ground potential for operating the control device, and a linkage mechanically connecting the operator and the control device. The linkage comprises a releasable coupling at a location of substantially line potential that is releasable to allow the control device to be operated independently of the operator. Latch means normally prevents coupling-release but is operable in response to predetermined electrical conditions to release the coupling and allow high-speed operation of the control device before the operator operates.

United States Patent [151 3,646,292 Barkan et al. 1 Feb. 29, 1972 [54] I HIGH-VOLTAGE ELECTRIC CIRCUIT 3,457,530. 7/1969 Van Sickle ..20p/l48 X BREAKER WITH HIGH-SPEED TRIPPING MEANS Primary ExaminerR. F. Staubly Attorney-J. Wesley Haubner, William Freedman. Frank L. [72] Inventors: Philip Barkan; Joseph W. Porter, both of Neuhauser, Oscar B. Waddell and Joseph B. Forman Media, Pa. 7 [73] Assignee: General Electric Company [57] ABSTRACT Discloses a high-Volta e circuit breaker com rising a control [22] Flled' May 1970 device at high potentifl operable to produce Separation of the [21] Appl. No.: 36,288 usual contacts of the breaker, an operator at ground potential for operating the control device, and a linkage mechanically connecting the operator and the control device. The linkage (g l Comprises a releasable coupling at a location of substantially [58] Fieid I78 82 B F 148 R line potential that is releasable to allow the control device to be operated independently of the operator. Latch means nor- [56] References Cited mally prevents coupling-release but is operable in response to predetermined electrical conditions to release the coupling UNITED STATES PATENTS and allow high-speed operation of the control device before the operator operates. 3,390,239 6/1968 Miller ..200/ I46 2,238,567 4/ l 941 Prince ..200/ 82 B 12 Claims, 7 Drawing Figures Patnted Feb. 29, "1972 4 Sheets-Sheet 1 w 5 v a in Patented Feb. 29, 1972 4 Sheets-Sheet 2 0 y z w w w w g L. flu f K 8 6 5 6 $1M a w P5 u 9 m 6 M I 6 o 9 M M 7 9 m M x7 W a a r F M MW 9 9 6 0 M Z \k 2 W a w N 3 To 2 a f 0. M

l/V VE/V 70/75 PHIL/P BA mm M, JOSEPH W Ponnm,

ATTORNEY Patented Fish. 29, 1972' 3,646,292

4 Sheets-Sheet 3 INVENTORS. PHIL/P BAR/(AN, Joann W Ponrm,

Arron/wry HIGH-VOLTAGE ELECTRIC CIRCUIT BREAKER WITH HIGH-SPEED TRIPPING MEANS BACKGROUND Thisinvention resulted from work done under Contract No. 14-03-9061 with Bonneville Power Administration in the Department of Interior and is subject to the terms and provisions of the Presidents Patent Policy Statement of Oct. 10, I963, 28 FR. 10943.

This invention relates to a high-voltage electric circuit breaker and, more particularly, to means for tripping open the circuit breaker at extra high speeds.

In the type of circuit breaker we are concerned with there is an interrupting assembly comprising separable contacts for connection in a high-voltage powerline and a control device operable to produce separation of said contacts. The interrupting assembly, including the control device, is at substantially line voltage and is electrically isolated from ground by an insulating column on which the interrupting assembly is mounted. For initiating operation of the control device, operating means at ground potential is provided and is coupled to the control device through linkage means of relatively great length extending between ground potential and line potential locations.

It is difficult to achieve extreme high-speed tripping with a long linkage of this type in view of the relatively great mass of such a linkage and the relatively long wave transmission time needed to transmit a stress wave from the operating means at ground potential to the control device at high potential.

' SUMMARY An object of out invention is to achieve high-speed circuit breaker tripping without the need for actuating the entire linkage prior to the tripping operation.

Another object is to provide linkage means between an operator at ground potential and a control device at high potential which includes a releasable coupling at high potential that can be released to permit circuit breaker tripping to occur at high speed without impedance from the major portion of the linkage means, which extends between high potential and ground.

Still another object is to provide a releasable coupling that can be incorporated into the linkage means to perform as in the first two objects without affecting the normal manner of closing the circuit breaker.

In carrying out the-invention in one form, we include in the linkage that connects the control device at high potential to the operator at ground potential a releasable coupling located in the high-potential region. The coupling, upon release, allows the control device to be operated independently of the operator. The coupling comprises a cylinder member and a piston member slidably mounted therein, one of said members being connected to the control device and the other to the operator. The cylinder and piston are located in a chamber normally filled with high-pressure gas. The cylinder has an end wall spaced from the piston, and the space tlierebetween is vented and sealed from the high-pressure gas in the chamber. Latch means normally prevents relative movement between the cylinder end wall and the piston and is operable to effect coupling-release. Such release allows the high-pressure gas in the chamber to drive the cylinder end wall and the piston relatively toward each other, thereby producing a contactseparating operation of said control device.

BRIEF DESCRIPTION OF DRAWINGS For a better understanding of the invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view of a high-voltage circuit breaker embodying one form of the invention.

FIG. 2 is a schematic view of the operating linkage present in the circuit breaker in FIG. 1. The circuit breaker is shown in its normal closed position.

FIG. 2a is a diagrammatic showing of a control used for the system of FIG. 2.

FIG. 3 is a schematic view of the operating linkage of FIG. 2 in a position through which it passes during a tripping operation.

FIG. 4 is a schematic view of the operating linkage of FIG. 2 in the fully open position of the circuit breaker.

FIG. 5 is a detailed showing of a portion of a slightly modified form of latch means for use in the linkage of FIG. 1-4.

FIG. 6 is a sectional view along the line 6-6 of FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT INTERRUPTING ASSEMBLY Referring now to FIG. 1, the circuit breaker shown therein comprises a metal tank 12 at high potential and a pair of conventional terminal bushings l3 and 14 projecting into the tank at its opposite ends. Each of these bushings comprises a conductive stud (not shown) extending axially thereof along its central longitudinal axis and connected at its outer end to the high-voltage circuit 15 in which the circuit breaker is connected. The tank 12 is filled with a high-pressure fluid, such as compressed air, which is used for circuit-interrupting purposes. Referring to FIG. 2, within the tank 12 is an interrupting assembly 16 that comprises a pair of separable contacts schematically shown at 17 and 18. Contact 18 is a movable contact that conductively bridges the space between the two stationary contacts 17. When the circuit breaker is closed, bridging contact 18 is in engagement with stationary contacts 17, thus permitting current to flow through the circuit 15 via contacts 17 and 18. Circuit interruption is effected by driving movable contact 18 downwardly to separate the contacts. This establishes an are between each pair of contacts, and this arc is extinguished in a well-known manner by the flow of pressurized gas from within the tank 12.

The interrupting assembly 16, as schematically shown in FIG. 2, comprises a fluid motor 20 comprising a cylinder 21 and a piston 22 reciprocably mounted within cylinder 21. Piston 22 is mechanically coupled to bridging contact 18 through a piston rod 24. A compression spring 25 biases piston 22 in an upward direction normally to hold bridging contact 18 in engagement with stationary contacts 17. The space beneath piston 22 is vented to atmosphere through a vent line 23.

When pressurized gas is supplied to cylinder space 26 above piston 22, an opening force is developed which drives piston 22 downwardly to separate contact 18 from contacts 17. For admitting pressurized gas into cylinder space 26, a control valve 27 is provided in an inlet line 28. This valve 27 is a conventional three-way valve that normally vents space 26 to atmosphere through a vent 29, but when valve 27 is operated, it closes off the vent 29 to atmosphere and connects the pressurized space within tank 22 to cylinder space 26. This allows pressurized gas to flow into space 26 to drive piston 22 downwardly through an opening stroke. For a specific example of a valve and fluid motor corresponding to those shown at 27 and 20, reference may be had to US. Pat. No. 2,783,338 to Beatty, assigned to the assignee of the present invention. The valve 27 and fluid motor 20 are occasionally referred to herein as a control device for the separable contacts.

OPERATING MEANS 32 AT GROUND POTENTIAL As shown in FIG. 1, the interrupter tank 12 is mounted atop a hollow insulating column 30 which electrically isolates the tank from ground. For operating the control valve 27 within tank 12, a fluid pressure operator 32 is provided at the bottom of insulating column 30 and is mechanically connected to the control valve through linkage means 35, as schematically shown in FIG. 2. This linkage means 35 comprises a long operating rod 36 that extends through the hollow insulating column 20 between its opposite ends. The operator 32 is at ground potential and the control device 27 is at substantially line potential. To provide the necessary electrical isolation between these parts, the operating rod 36 is of suitable insulating material. The operator 32 is located within a grounded casing 33 (FIG. 1) at the bottom of insulating column 30.

Operator 32 comprises a cylinder 40 and a piston 41 slidably mounted therein. The cylinder space to the left of piston 41 is normally vented to atmosphere. Opening of a circuit breaker can be effected by driving piston 41 to the left from its position of FIG. 2. This is done by supplying pressurized fluid to the space 43 at the right of piston 41. A threeway control valve 45 controls the pressure in space 43, normallyventing the space to atmosphere. When, however, valve 45 is operated, it moves into its position of FIG. 3 to connect the high-pressure air supply line 47 with cylinder line 48, thereby supplying pressurized fluid to the cylinder space 43. This drives piston 41 to the left through a normal opening stroke...

Control valve 45 comprises a movable valve element 49 that is biased by a tension spring 49a into its venting position of FIG. 2. The movable valve element 49 is operable by a solenoid 50, which upon energization drives the valve element 49 clockwise into the position of FIG. 3 to interconnect highpressure line 47 and line 48. The solenoid 50 has its coil connected across a pair of supply terminals 52 and 53 and in series with a normally open switch 55. When switch 55 is operated to closed position, in a manner soon to be described, it completes an energizing circuit between terminals 52 and 53 to operate the solenoid and valve element 49 into their position of FIG. 3. A suitable latch 57, referred to herein as the closing control latch, holds the solenoid and movable valve element 49 in their position of FIG. 3 until intentionally released for a subsequent closing operation, as will soon be described. A normally open trip-initiating switch 58, which may be controlled either manually or in response to predetermined conditions, shunts the switch 55 and can be closed, instead of switch 55, to complete the energizing circuit for solenoid 50.

The closing-control latch 57, which holds the solenoid 50in its operated position,.is biased toward a latching position by spring 570 but can move into its latching position only when the solenoid 50 is operated. Closing-control latch 57 is releasable by a suitable closing-control solenoid 59 having its coil connected in a closing-control circuit 59a. Referring to FIG. 4, when closing-control circuit 59a is closed, it operates solenoid 59 to release latch 57, thus allowing the control valve 45 to return to its venting position. This produces a closing of the circuit breaker, as will soon be described.

LINKAGE 35 BETWEEN OPERATING MEANS 32 AND CONTROL DEVICE 27, 20

Returning to linkage means 35, this linkage means further comprises two horizontal rods 60 and 61 joined together by a lost motion coupling 62. Rod 60 is mechanically connected at its left-hand end to piston 41 and at its right-hand end to a cylindrical cage 63 forming a part of the lost motion coupling 62. Within cylindrical cage 63 is a piston 64 that can move horizontally with limited lost motion in the cage. A compression spring 65 biases piston 64 to the left, normally holding it against left-hand end wall 67, as shown in FIG. 2. When piston 41 of operator 32 is driven to the left from its position of FIG. 1, it drives cage 63 to the left, compressing spring 65 and transmitting force through the spring to piston 64, thereby driving rod 61 to the left.

For converting horizontal movement of rod 61 into vertical movement of insulating rod 36, a crank 70 is provided. Crank 70 is pivotally mounted on a stationary pivot 71 and has one arm pivotally connected at 72 to horizontal rod 61 and its other arm pivotally connected at 74 to vertical rod 36.

RELEASABLE COUPLING 75 The upper end of operating rod 36 is connected through a releasable coupling 75 to a rod 76 that is connected to control valve 27. Releasable coupling 75 comprises a cylinder 80 having an end wall 81 at its lower end that is connected to operating rod 36. Slidably mounted within cylinder 80 is a piston 83 that is connected to valve actuating rod 76. A releasable latch 85 normally locks the cylinder 80 and piston 83 together.

The latch 85 comprises a movable latching member 86 that is slidably mounted for horizontal motion in a housing 87 that is secured to cylinder 80. The latching member 86 has a disc 116 fixed thereto at its outer end. A compression spring 110 acting against a shoulder 112 on latching member 86 biases latching member 86 to the left into a notch 113 in the outer periphery of piston 83. A coil 114 mounted on housing 87 is used for developing a latch-releasing force. When energized, coil 114 develops a repulsive force on disc 116 that drives the disc and latching member 86 to the right to release the latch. The latch means which comprises latch 85 further comprises a stop 89 fixed to the cylinder 80 in a position within its bore immediately adjacent the upper surface of piston 83 so as toprevent upward movement of piston 83 relative to cylinder 80 past the position shown in FIG 2. The purpose of stop 89 will soon appear more clearly.

As shown in FIG. 2, the releasable coupling 75 is located within a small chamber 88 that is normally filled with pressurized gas derived from tank 12. The walls of chamber 88 are defined by a cylindrical metal housing 90 located atop insulating column 30 and secured to the bottom of interrupter tank 12. Preferably chamber 88 freely communicates with the interior of tank 12. For guiding the cylinder 80 and providing a seal about its outer cylindrical surface, a tubular guide 92, fixed to housing 90, is provided. This guide 92 has a bore which slidably receives cylinder 80. The bore has an enlarged portion 94 that is freely vented to atmosphere through a passage 95. A port in the cylinder 80 always communicates with vented portion 94, thus maintaining the cylinder space 96 between piston 83 and end wall 81 vented to atmosphere. The space beneath end wall 81 is always in communication with the high-pressure gas in chamber 88 by reason of passages 97 in guide 92. Likewise, the space above piston 83 is always in communication with the high-pressure gas in chamber 88. The vented cylinder space 96 is sealed from the high-pressure gas in chamber 88 by means of O-ring seals 98 and 99 between the relatively movable parts'of the coupling.

When latch 85 is set, as shown in FIG. 2, the downward forces on cylinder 81 are balanced by the upward forces on piston 83, and a condition of stable equilibrium exists. As will soon be described under High-Speed Tripping," this equilibrium condition is upset when the latch 85 is released, resulting in the simultaneous application of a downward accelerating force to piston 83 and an upward accelerating force to cylinder wall 81.

For normally holding the parts of linkage 35 in their position of FIG. 2 when the circuit breaker is closed, a compression spring 100 within tank 12 acts against a shoulder 102 on the valve-actuating rod 76. This spring biases rod 76 upwardly into its elevated position of FIG. 2.

HIGH SPEED TRIPPING A high-speed tripping operation is effected by releasing the latch 85 in a manner soon to be described, thus uncoupling piston 83 from cylinder 80. This allows the high-pressure gas acting on the top surface of piston 83 to rapidly drive the piston downwardly against the bias of spring 100 into the position of FIG. 3, thereby opening the control valve 27 to cause motor 20 to separate the contacts 17, 18, as shown in FIG. 3. A suitable dashpot (not shown) cooperating with rod 76 terminates this downward motion of piston 83 when the piston reaches its position of FIG. 3.

Concurrently with this rapid downward movement of piston 83, the cylinder 80, in response to release of latch 85, is driven upwardly through a short stroke by the high-pressure gas acting beneath its end wall 81. This upward movement lifts the operating rod, 36 and drives horizontal rod 61 a short distance to the right against the bias of spring 65 in lost motion connection 62. This movement to the right of horizontal rod 61 causes a cam 104 on rod 61 to close switch 55, thus energizing solenoid 50. Solenoid 50 responds by operating valve 45, causing operator 32 to drive its piston 41 to the left through a normal opening stroke.

The above-described motion of piston 41 to the left serves, following a high-speed tripping operation, to reset the releasable coupling 75. More specifically, such movement drives cylinder 80 downwardly from its position of FIG. 3 toward its position of FIG. 4, carrying latch 85 therewith. When cylinder 80 enters the position of FIG. 4, the movable latch member 86 again aligns with notch 113 in the piston and is therefore free to reset the leftward bias of reset spring 110.

From the above description of a high-speed tripping operation, it should be apparent that we are able to effect such tripping without the need for first actuating most of the linkage 35. Only the extreme upper portion of the linkage, i.e., piston 83 and valve actuating rod 76, is required to operate in order to effect opening of the control valve 27 during such high-speed tripping. The remainder of the linkage, i.e., the cylinder 80, operating rod 36, crank 70, and all of the lower mechanism 61, 62, 60, 41, is able to remain stationary, or even more in an opposite direction, during this interval without impeding such high-speed tripping. Thus, we eliminate the need for accelerating most of the mass of the linkage and the need for transmitting a stress wave over the long distance between opposite ends of the linkage 35 in order to effect tripping.

NORMAL TRIPPING If it is sufficient to trip the circuit breaker at the usual lower speed, this can be done without relying upon release of latch 85 and simply by closing the trip-initiating switch 58. This operates the ground-level fluid motor 32, causing it to actuate the entire linkage 35, thereby supplying opening force to valve 27 through the entire linkage. It is to be noted that the presence of the releasable coupling 75 results in no significant added forces on the linkage during such low speed tripping; This is the case because so long as the latch 85 is set, the force produced by the high-pressure gas acting upwardly on the cylinder end wall 81 is balanced by the force produced by the high pressure acting downwardly on the piston 83.

During the above-described normal tripping action, the stop 89 on cylinder 80 bears against the upper surface of piston 83 to assure that the piston moves downwardly with the cylinder 80 and that latch means 85, 89 remains set.

CONTROL FOR INITIATING HIGH-SPEED TRIPPING Referring to FIG. 2a, the energy for tripping latch 85 is preferably derived from a suitably charged capacitor 120 located in the high-potential region of the circuit breaker. Across the terminals of this capacitor, the coil 114 is connected in series with a normal-off switching device such as a light-activated SCR 117. When the switching device 117 is turned on, the capacitor 120 discharges through the solenoid coil 114 to release the latch 85.

For supplying a light signal to the light-activated SCR 117 in order to turn it on, a light pipe 124, preferably of fiber optics, is connected between the SCR and a normally off light source 121 at ground potential. When light source 121 is turned on, it emits a pulse of light that is transmitted through light pipe 124 to the SCR 117, abruptly turning on the SCR. The capacitor 120 responds to this turn by rapidly discharging through the SCR and the solenoid coil 114 to quickly operate the solenoid.

Although in the illustrated embodiment, the trip-initiating signal for the circuit breaker must be transmitted over the relatively great distance between ground and the high-voltage line, it is capable of traversing this distance without significant time delay since it travels at the speed of light. The light source 121 is preferably a device, such as a Xenon gas lamp, capable of emitting a pulse of light with a steep rate of rise of luminous intensity so that there is no significant delay in turning on the SCR after the pulse arrives at the SCR. Since the light pipe is a long member of electrical insulating material, it is capable of easily withstanding the high line-to-ground voltage present between its ends. Light source 121 is turned on by a signal derived from suitable condition-responsive means (not shown) such as protective relaying means coupled to line 15.

Although we have shown light-responsive means, partially at ground potential, for initiating high-speed tripping, it is to be understood that other suitable high-speed trip-initiating means could be used, e.g., overcurrent-responsive means, such as a series-coil, located entirely in the high-potential region ofthe circuit breaker.

CIRCUIT BREAKER CLOSING A circuit breaker closing operation is effected by venting the cylinder space 43 in the operator 32 when the mechanism is in its open position of FIG. 4. Such venting is effected by tripping closing-control latch 57 to release solenoid 50 and allow spring'49a to return control valve 45 to its venting position of FIG. 2. Closing control latch 57 is tripped by completing circuit 59a by means ofa closing control switch 59b.

When the cylinder space 43 is thus vented, the spring at the upper end of the linkage 35 responds by operating the valve 27 to its venting position, thus venting cylinder space 26 and allowing spring 25 in fluid motor 20 to close the contacts 17, 18. When the spring 100 discharges in this manner to operate the valve 27, it returns the parts of linkage 35 to their position of FIG. 2. During this closing operation, coupling 75 acts as a rigid link between the valve-actuating rod 76 and the operating rod 36 since latch means 85, 89 remains set during this interval, as shown in FIG. 4, where it can be seen that stop 89 will prevent piston 83 from moving upwardly relative to cylinder 80. Accordingly, closing takes place in the same manner as it would if the coupling 75 was not present and a simple rigid link was instead present for coupling together rods 36 and 76.

MODIFIED LATCH OF FIGS. 5 AND 6 In the releasable coupling 75 of FIGS. 2-4, we have, for simplification, shown latching means 85 as comprising a simple pin of appropriate shape cooperating with the notch 113 in the piston 83. However, a preferred form of latch is illustrated in FIGS. 5 and 6. Here, the latch comprises a split ring ofcircular cross section that is carried in an annular groove 134 in the piston 83. This piston ring 130 is a resilient member that has a tendency to expand in diameter, but its expansion is limited by the internal wall of cylinder 80 and specifically by a conical shoulder 132 on the internal wall of cylinder 80. Downward force on piston 83 is transmitted to the piston ring through groove surface 133 and urges the piston ring against conical shoulder 132. The reaction force developed on the ring by the conical shoulder tends to contract the ring. The ring is normally prevented from contracting beyond the position shown in FIG. 6 by a latching member 138, shown in FIG. 5, that fits between the ends of the split ring. When latching member 138 is withdrawn radially outward from this position, the reaction force from conical shoulder 132 on the ring forces the ring to contract completely into groove 134, thus releasing the piston for downward movement. An advantage of this type of latch is that the latching force on the piston is well distributed around the periphery of the piston and also a relatively small releasing force can be used to release a very large force on the piston 83.

ADDITIONAL COMMENTS It is to be understood that the parts shown in the schematic illustrations of FIGS. 2-4 are not shown to scale. For example, the operator 32, despite appearing smaller than coupling 75, is in an actual device larger and thus is readily capable of developing enough force to function in the manner described hereinabove.

While we have shown and described a particular embodiment of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention in its broader aspects; and we, therefore, intend herein to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker for a high-voltage line comprising:

a. an interrupting assembly normally at substantially line potential comprising separable contacts for connection in said line and a control device operable to produce separation of said contacts,

b. insulating structure supporting said interrupting assembly and electrically isolating said assembly, including said control device, from ground,

c. operation means for said control device at substantially ground potential,

d. linkage means mechanically connecting said operating mans and said control device,

e. said linkage means comprising a cylinder member and a piston member slidably mounted therein, one of said members being mechanically connected to said control device and the other being mechanically connected to said operating means,

1. said cylinder and piston be located in a chamber normally filled with high-pressure gas, said cylinder having an end wall spaced from said piston,

g. means venting the cylinder space between said piston and said end wall to a lower pressure region and means for sealing said vented cylinder space from the high-pressure gas in said chamber,

h. said cylinder end wall and piston having surfaces on which the high-pressure gas in said chamber can act to drive said end wall and said piston relatively toward each other, thereby producing a contact-separating operation of said control device,

i. latch means normally preventing relative movement between said piston and said cylinder end wall, maintaining a predetermined spacing between said piston and end wall, and releasable to allow the high-pressure gas in said chamber to drive said end wall and said piston relatively toward each other, thereby producing contact-separating operation of said control device, and

j. means responsive to predetermined electrical conditions for releasing said latch means to allow high-speed operation of said control device before said operating means operates.

2. The circuit breaker of claim 1 in combination with means effective after said relative motion of said piston and end wall toward each other for causing said operating means to operate to separate said end wall and piston and thereby reset said latch means while said contacts are in a separated position.

3. The circuit breaker of claim 2 in which said latch means comprises a portion mounted on said cylinder for movement therewith and a portion mounted on said piston for movement therewith.

4. The circuit breaker of claim 2 in combination with means for driving said linkage means through a closing stroke during a closing operation of said circuit breaker, said latch means remaining set during said closing stroke to maintain a fixed spacing between said piston and cylinder end wall during said closing stroke.

5. The circuit breaker of claim 1 in which said cylinder and piston are located in a region of the circuit breaker that is normally at substantially line potential.

6. The circuit breaker of claim 5 in combination with means effective after said relative motion of said piston and end wall toward each other for causing said operating means to operate to separate said end wall and piston and thereby reset said latch means while said contacts are in a separated position.

7. The circuit breaker of claim 5 in combination with means responsive to relative motion of said end wall and piston toward each other for causing said operating means to operate to separate said end wall and piston and thereby reset said latch means while said contacts are in separated position.

8. The circuit breaker of claim 5 .in which:

a. the piston or cylinder member that is connected to said control device moves in a direction to decrease the spacing between said piston and end wall in response to tripping of said latch means, and

b. there is provided means effective after said spacing is decreased for causing said operating means to drive the piston or cylinder member that is connected to said operating means in a direction to increase the spacing between said piston and end wall and thereby reset said latch means,

c. said space-increasing motion occuring while said contacts are in a separated position. v

9. The circuit breaker of claim 5 in combination with means for driving said linkage means through a closing stroke during a closing operation of said circuit breaker, said latch means remaining set during said closing stroke to maintain a fixed spacing between said piston and said cylinder end wall during said closing stroke.

l0.' The circuit breaker of claim 1 in which said piston has a circumferentially extending groove in its periphery and said latch means comprises a split ring located in said groove and a radially movable latching member located between the ends of said ring, said split ring engaging an annular shoulder on said cylinder tending to force said ring to contract within said groove into a noninterfering position with respect to said shoulder, said contraction normally being prevented by said latching member but occurring in response to withdrawal of said latching member from its position between the ends of said split ring.

11. An electric circuit breaker for a high-voltage line comprising:

a. an interrupting assembly normally at substantially line potential comprising separable contacts for connection in said line and a control device operable to produce separation of said contacts,

b. insulating structure supporting said interrupting assembly and electrically isolating said assembly, including said control device, from ground,

c. operating means for said control device at substantially ground potential,

d. linkage means mechanically connecting said operating means and said control device,

e. said linkage means comprising a releasable coupling located in a region normally at substantially line potential and releasable to allow said control device to be operated independently of said operating means to produce separation of said contacts,

f. latch means normally preventing release of said coupling and operable to permit said release,

g. means responsive to predetermined electrical conditions for operating said latch means to release said coupling and allow high speed operation of said control device before said operating means operates,

g. means for operating said control device independently of said operating means of (c) in response to release of said coupling,

h. and means for causing said operating means to operate to reset said coupling while said contracts are in a separated position.

12. The circuit breaker of claim 11 in which:

a. said releasable coupling comprises a pair of relatively movable members, one connected to said control device and one connected to said operating means,

b. said latch means has a portion mounted on one of said members for movement therewith and another portion mounted on the other of said members for movement therewith for maintaining a predetermined spacing between said members when said latch means is set,

c. the means of (g') of claim 11 comprises fluid pressure means acting on the member connected to said control device for operating said control device in response to a releasing operation of said latch means, thereby decreasing the spacing between said members,

d. and the means of (h) of claim 1 1 comprises means effec- 

1. An electric circuit breaker for a high-voltage line comprising: a. an interrupting assembly normally at substantially line potential comprising separable contacts for connection in said line and a control device operable to produce separation of said contacts, b. insulating structure supporting said interrupting assembly and electrically isolating said assembly, including said control device, from ground, c. operation means for said control device at substantially ground potential, d. linkage means mechanically connecting said operating mans and said control device, e. said linkage means comprising a cylinder member and a piston member slidably mounted therein, one of said members being mechanically connected to said control device and the other being mechanically connected to said operating means, f. said cylinder and piston be located in a chamber normally filled with high-pressure gas, said cylinder having an end wall spaced from said piston, g. means venting the cylinder space between said piston and said end wall to a lower pressure region and means for sealing said vented cylinder space from the high-pressure gas in said chamber, h. said cylinder end wall and piston having surfaces on which the high-pressure gas in said chamber can act to drive said end wall and said piston relatively toward each other, thereby producing a contact-separating operation of said control device, i. latch means normally preventing relative movement between said piston and said cylinder end wall, maintaining a predetermined spacing between said piston and end wall, and releasable to allow the high-pressure gas in said chamber to drive said end wall and said piston relatively toward each other, thereby producing contact-separating operation of said control device, and j. means responsive to predetermined electrical conditions for releasing said latch means to allow high-speed operation of said control device before said operating means operates.
 2. The ciRcuit breaker of claim 1 in combination with means effective after said relative motion of said piston and end wall toward each other for causing said operating means to operate to separate said end wall and piston and thereby reset said latch means while said contacts are in a separated position.
 3. The circuit breaker of claim 2 in which said latch means comprises a portion mounted on said cylinder for movement therewith and a portion mounted on said piston for movement therewith.
 4. The circuit breaker of claim 2 in combination with means for driving said linkage means through a closing stroke during a closing operation of said circuit breaker, said latch means remaining set during said closing stroke to maintain a fixed spacing between said piston and cylinder end wall during said closing stroke.
 5. The circuit breaker of claim 1 in which said cylinder and piston are located in a region of the circuit breaker that is normally at substantially line potential.
 6. The circuit breaker of claim 5 in combination with means effective after said relative motion of said piston and end wall toward each other for causing said operating means to operate to separate said end wall and piston and thereby reset said latch means while said contacts are in a separated position.
 7. The circuit breaker of claim 5 in combination with means responsive to relative motion of said end wall and piston toward each other for causing said operating means to operate to separate said end wall and piston and thereby reset said latch means while said contacts are in separated position.
 8. The circuit breaker of claim 5 in which: a. the piston or cylinder member that is connected to said control device moves in a direction to decrease the spacing between said piston and end wall in response to tripping of said latch means, and b. there is provided means effective after said spacing is decreased for causing said operating means to drive the piston or cylinder member that is connected to said operating means in a direction to increase the spacing between said piston and end wall and thereby reset said latch means, c. said space-increasing motion occuring while said contacts are in a separated position.
 9. The circuit breaker of claim 5 in combination with means for driving said linkage means through a closing stroke during a closing operation of said circuit breaker, said latch means remaining set during said closing stroke to maintain a fixed spacing between said piston and said cylinder end wall during said closing stroke.
 10. The circuit breaker of claim 1 in which said piston has a circumferentially extending groove in its periphery and said latch means comprises a split ring located in said groove and a radially movable latching member located between the ends of said ring, said split ring engaging an annular shoulder on said cylinder tending to force said ring to contract within said groove into a noninterfering position with respect to said shoulder, said contraction normally being prevented by said latching member but occurring in response to withdrawal of said latching member from its position between the ends of said split ring.
 11. An electric circuit breaker for a high-voltage line comprising: a. an interrupting assembly normally at substantially line potential comprising separable contacts for connection in said line and a control device operable to produce separation of said contacts, b. insulating structure supporting said interrupting assembly and electrically isolating said assembly, including said control device, from ground, c. operating means for said control device at substantially ground potential, d. linkage means mechanically connecting said operating means and said control device, e. said linkage means comprising a releasable coupling located in a region normally at substantially line potential and releasable to allow said control device to be operated independently of said operating means to produce separation of sAid contacts, f. latch means normally preventing release of said coupling and operable to permit said release, g. means responsive to predetermined electrical conditions for operating said latch means to release said coupling and allow high speed operation of said control device before said operating means operates, g''. means for operating said control device independently of said operating means of (c) in response to release of said coupling, h. and means for causing said operating means to operate to reset said coupling while said contracts are in a separated position.
 12. The circuit breaker of claim 11 in which: a. said releasable coupling comprises a pair of relatively movable members, one connected to said control device and one connected to said operating means, b. said latch means has a portion mounted on one of said members for movement therewith and another portion mounted on the other of said members for movement therewith for maintaining a predetermined spacing between said members when said latch means is set, c. the means of (g'') of claim 11 comprises fluid pressure means acting on the member connected to said control device for operating said control device in response to a releasing operation of said latch means, thereby decreasing the spacing between said members, d. and the means of (h) of claim 11 comprises means effective after said decrease in spacing for causing said operating means to operate to reestablish said predetermined spacing between said members, thereby resetting said latch means while said contacts are in a separated position. 